A clutch is applied to vehicles in order to connect and disconnect driving force of an engine boarded on a vehicle in a process of transmitting the driving force to driving wheels. A known twin clutch transmission having two clutches is described in JP2003-120764. Generally, a twin clutch transmission includes a first clutch for connecting a first input shaft to an engine, and a second clutch for connecting a second input shaft to the engine. The first input shaft and the second input shaft include plural driving gears having different gear ratio, respectively, and one of the plural driving gears is configured to be engaged with a driven gear of an output shaft. In case a gear is shifted, for example, when gears are shifted from a traveling state where one of driving gears of the first input shaft is engaged and the first clutch is engaged to a state where the engaged gear is shifted to another driving gear of the second input shaft, temporarily, the driving force is shared to be transmitted by means of the both first and second clutches. In other words, a transmitting path of the driving force is shifted from the first clutch to the second clutch by gradually reducing engagement ratio of the first clutch, simultaneously, by gradually increasing engagement ratio of the second clutch from a state where the first clutch is completely engaged and the second clutch is disengaged, and, eventually the complete driving force is transmitted by the second clutch.
Thus, a twin clutch transmission is advantageous in terms of enabling to shift gears smoothly without interrupting transmission of driving force, and of enabling to construct a transmission to have more number of different gear ratios, that is, more number of speeds can be provided compared to a single clutch transmission.
Meanwhile, when a vehicle is suddenly started, a driving force transmission system is likely damaged and driving wheels likely slips because a clutch is suddenly engaged at a state where driving force is increased by increasing engine rpm by opening a throttle. Those disadvantages are common to a twin clutch transmission and a single clutch transmission, and as a counter measurement, driving force of the engine is limited by means of fuel cut and slow engagement operation of the clutch by manual operation. Further, in order to prevent a slip of driving wheels caused by the excessive driving force during the vehicle travels and at a start of the vehicle on rough road such as gravel road which is not paved and snowy or icy road, driving force is controlled by the fuel cut and an anti-lock braking system (ABS), or the like.
Notwithstanding, there is a restriction in terms of time response with the foregoing method, and start control for increasing speed in a short time by controlling the driving force immediately and appropriately has not been achieved. Further, start control and traveling control adapted to conditions such as specification differences among vehicles, personal habits of drivers, and road conditions have not been achieved.
A need thus exists for a transmission having plural clutches which can control driving force immediately and appropriately to prevent driving wheels from slipping when a vehicle starts on a rough road, starts suddenly and travels on rough road, and excels in economical efficiency.